The present invention relates to the construction of micro-electro mechanical devices such as ink jet printers.
In international patent application PCT/AU98/00550, the present applicant has proposed an ink jet printing device which utilizes micro-electro mechanical (MEMS) processing techniques in the construction of a print head driven by thermal bend actuator devices for the ejection of fluid such as ink from an array of nozzle chambers.
Devices of this type have a number of limitations and problems.
It is an object of the present invention to provide various aspects of an inkjet printing device which overcomes or at least ameliorates one of or more of the disadvantages of the prior art or which at least offers a useful alternative thereto.
According to a first aspect of the invention, there is provided a micro-electromechanical fluid ejection device that comprises
a substrate;
a nozzle chamber wall and a roof wall that are positioned on the substrate to define a nozzle chamber and an ink ejection port in the roof wall, a fluid being receivable in the nozzle chamber;
an elongate actuator arm having a fixed end portion that is fast with the substrate and a free end portion that is spaced from the substrate, the elongate actuator arm incorporating a heating circuit that is connectable to a power supply to heat the actuator arm, at least a portion of the actuator arm being of a material having a coefficient of thermal expansion which is such that the material is capable of thermal expansion to do work, the heating circuit being positioned to generate differential thermal expansion and contraction when heated and subsequently cooled to cause reciprocal displacement of the free end portion of the actuator arm;
a fluid ejection member that is fast with the free end of the elongate actuator arm to be positioned in the nozzle chamber such that said displacement of the free end portion of the actuator arm results in the ejection of fluid from the ink ejection port; and
control logic circuitry positioned on the substrate along an elongate region defined on the substrate and interposed between the actuator arm and the substrate, the control logic circuitry being connected to the heating circuit to enable and disable the power supply according to a control signal received by the control logic circuitry.
The elongate actuator arm may be a laminated structure having a first metal layer and a dielectric layer, the first metal layer being interposed between the dielectric layer and the substrate and defining the heating circuit.
The actuator arm may have a second metal layer that is positioned so that the dielectric layer is interposed between the metal layers, said second metal layer being substantially the same as the first metal layer.
The metal layers and the dielectric layer may project from the free end of the actuator arm to define the fluid ejection member. A discontinuity may be defined in the first metal layer between the heating circuit and the fluid ejection member.
The control logic circuitry may define transfer register circuitry to receive control signals and drive transistor circuitry connected to the transfer register circuitry. The drive transistor circuitry may be interposed between the heating circuit and the substrate and may be defined by a plurality of traces that are positioned to extend transversely with respect to a longitudinal axis of the actuator arm.
The invention extends to a printhead which comprises a plurality of micro-electromechanical fluid ejection devices as described above.
In accordance with a second aspect of the present invention, there is provided an inkjet printhead having a series of nozzles for the ejection of ink wherein each said nozzle has a rim formed by the conformal deposition of a rim material layer over a sacrificial layer and a subsequent planar etching of at least said rim material layer so as to form said nozzle rim.
The planar etching can comprise chemical-mechanical planarization of the rim material layer and any associated sacrificial layers.
In accordance with a third aspect of the present invention, there is provided an inkjet printhead comprising:
a plurality of nozzle chambers each having an ink ejection aperture in one wall thereof and an actuator interconnection aperture in a second wall thereof;
a moveable ink ejection paddle located within the nozzle chamber and moveable under the control of an external thermal actuator through said actuator interconnection aperture for the ejection of ink out of said ink ejection aperture;
said external actuator being covered by a protective covering shell around the operational portions of said actuator, spaced apart from said actuator.
The protective covering shell can be formed simultaneously with the formation of other portions of the inkjet printing arrangement in particular with the nozzle chamber walls.
The external actuator can comprise a thermal bend actuator.
In accordance with a third aspect of the present invention, there is provided a method of forming an inkjet printhead on a substrate said method including:
providing a first substrate on which is formed electrical drive circuitry made up of one or more interleaved layers of conductive, semi-conductive and non-conductive material for the control of said inkjet printed;
forming on said substrate at least one nozzle chamber having an ink ejection aperture in one wall thereof;
providing a moveable ink ejection paddle within said nozzle chamber, moveable under the control of an actuator for the ejection of ink out of said ink ejection aperture;
and utilizing portions of at least one of said interleaved layers as a sacrificial material layer in the formation of one or more of the group comprising said actuator and said ink ejection paddle.
The sacrificial material layer can comprise portions of a conductive layer of the electrical drive circuitry. The electrical drive circuitry can comprise a Complementary Metal Oxide (CMOS) process and the sacrificial material layer can comprise a CMOS metal layer.
The sacrificial material layer can be utilized in formulating the actor. The actuator can comprise a thermal actuator. The actuator can be located external to the nozzle chamber and can be interconnected to the ink ejection paddle through an actuation interconnection aperture formed in a second wall of the nozzle chamber.
In accordance with a fourth aspect of the present invention, there is provided an inkjet printhead constructed by MEMS processing techniques with a plurality of ink ejection nozzles each having a nozzle chamber, an external thermal bend actuator having a proximal end anchored to a substrate and a distal end connected to an ink ejection paddle within said chamber;
wherein said external thermal bend actuator further comprises a series of layers and includes a planar conductive heating circuit layer which includes a first portion adjacent said proximal end forming a planar conductive heating circuit for heating said thermal bend actuator, and a second portion extending into said ink ejection paddle, said second portion being electrically isolated from said first portion by means of a discontinuity in said planar conductive heating circuit layer, said discontinuity being located external to said nozzle chamber.
The planar conductive heating circuit layer can comprise substantially titanium nitride. The conductive circuit preferably can include at least one tapered portion adjacent the proximal end so as to increase resistive heating adjacent the proximal end.
In accordance with a fifth spect of the present invention, there is provided an inkjet printhead having a series of ink ejection nozzles for the ejection of ink, each of said nozzles interconnecting a nozzle chamber with an external atmosphere, each said nozzle having a first meniscus rim around which an ink meniscus normally forms, and an extended ink flow prevention rim spaced outwardly from said first meniscus rim and substantially encircling said first meniscus rim, arranged to prevent the flow of ink across the surface of said inkjet printhead.
The ink flow prevention rim can be substantially co-planar with the first meniscus rim and can be formed from the same material as the first meniscus rim.
The ink flow prevention rim and the first meniscus rim are preferably formed utilizing chemical mechanical planarization.
The ink flow prevention rim and the first meniscus rim are preferably formed from Titanium Nitride.
In accordance with a sixth aspect of the present invention, there is provided a moveable micromechanical device including a bend actuator adapted to curve in a first bending direction and having a substantially planar bottom surface, said bend actuator being formed on a plane substrate on top of a number of deposited lower layers, wherein the bend actuator is formed by a plurality of steps including:
forming a series of structures in said deposited lower layers, said series of structures having a surface profile including a series of elongate ribs running in a direction substantially transverse to said first bending direction.
The bend actuator can comprise a thermal bend actuator. The deposited layers can include a conductive circuitry layer and can be interconnected to the bend actuator for activation of the bend actuator. The bend actuator can be attached to a paddle member and actuated for the ejection of ink from an ink ejection nozzle of an inkjet printhead. The deposited layer, located under the bend actuator can include a power transistor for the control of operation of the bend actuator.
In accordance with a seventh aspect of the present invention, there is provided a method of construction of an inkjet printhead having a large array of inkjet nozzle arrangements said method comprising:
defining a single inkjet nozzle arrangement for the ejection of ink from a single nozzle; and
utilizing a series of translations and rotations of said single inkjet nozzle arrangement to form all the inkjet nozzles of said inkjet print head;
said utilizing step including:
initially forming a plurality of nozzles in a pod;
forming a group of pods, each group corresponding to a different colored ink dispensed from said printhead;
forming a plurality of said groups of pods into a firing group;
combing firing groups forming a segment of said printhead;
forming each segment together to form said printhead.
The inkjet nozzle arrangements can include a series of layers deposited and etch utilizing a mask. The layers can include conductive layers which are preferably etched utilizing the mask so as to form a series of conductive interconnections. The conductive interconnects can include interconnects with adjacent versions of the inkjet nozzle arrangement which can comprise translated and/or rotated copies of the inkjet nozzle arrangement.
In accordance with an eighth aspect of the present invention, there is provided a method of operation of a fluid ejection printhead within a predetermined thermal range so as to print an image, said printhead including a series of thermal actuators operated to eject fluid from said printhead, said method comprising the steps of:
(a) sensing the printed temperature of said printhead to determine if said printhead temperature is below a predetermined threshold,
(b) if said printhead temperature is below said predetermined threshold, performing a preheating step of heating said printhead so that it is above said predetermined threshold,
(c) controlling said preheating step such that said thermal actuators are heated to an extent insufficient to cause the ejection of fluid from said printhead; and
(d) utilizing said printhead to print said image.
The step (a) can further preferably include the steps of: (aa) initially sensing an ambient temperature surrounding the printhead, (ab) setting the predetermined threshold to be the ambient temperature plus a predetermined operational factor amount, the operational factor amount being dependant on the ambient temperature.
The method can further comprise the step of: (d) monitoring the printhead temperature whilst printing the image and where the temperature falls below the predetermined threshold, reheating the printhead so that it can be above the predetermined threshold.
The step (b) can comprise constantly monitoring the printhead temperature whilst heating the printhead.
The step (c) further can comprise applying a series of short electrical pulses so the thermal actuators, each being insufficient to cause the ejection of fluid from the printhead.
In accordance with an additional aspect of the eighth aspect of the present invention, there is provided a fluid ejection device comprising:
an array of nozzles formed on a substrate and adapted to eject ink on demand by means of a series of ink ejection thermal actuators actuated by an actuator activation unit attached to said ink ejection actuators for activation thereof;
at least one temperature sensor attached to said substrate for sensing the temperature of said substrate; and
a temperature sensor unit;
wherein before a fluid ejection operation is begun said temperature sensor unit utilizes said at least one temperature sensor to sense a current temperature of said substrate, and if said temperature is below a predetermined limit, to output a preheat activation signal to said actuator activation unit, whereupon said actuator activation unit activates said ink ejection thermal actuators to an extent sufficient to heat said substrate, while being insufficient for the ejection of ink from said array.
The at least one temperature sensor can comprise a series of spaced apart temperature sensors formed on the print head.
The array of nozzles are preferably divided into a series of spaced apart segments with at least one temperature sensor per segment.
In accordance with a ninth aspect of the present invention, there is provided an ink supply arrangement for supplying ink to the printing arrangement of a portable printer, said ink supply arrangement including:
an ink supply unit including at least one storage chamber for holding ink for supply to said printing arrangement, said ink supply unit including a series of spaced apart baffles configured so as to reduce the acceleration of the ink within the unit as may be induced by movement of the portable printer, whilst allowing for flows of ink to the printing arrangement in response to active demand therefrom.
Preferably, the ink printing arrangement is in the form of a printhead which is connected directly to an ink supply arrangement in the form of an ink supply unit having an ink distribution manifold that supplies ink via a plurality of outlets to corresponding ink supply passages formed on the printhead.
In the preferred form, the printhead is an elongate pagewidth printhead chip and the baffles in the ink supply are configured to reduce acceleration of the ink in a direction along the longitudinal extent of the printhead and corresponding ink supply unit. Preferably, the ink supply unit has a series of storage chambers for holding separate color inks.
Preferably, the ink storage chamber or chambers arm constructed from two or more interconnecting molded components.
In accordance with a tenth aspect of the present invention, there is provided a power distribution arrangement for an elongate inkjet printhead of a kind having a plurality of longitudinally spaced voltage supply points, said power distribution arrangement including:
two or more elongate low resistance power supply busbars; and
interconnect means to connect a selected plurality of said voltage supply points to said busbars.
Preferably the busbars are disposed to extend parallel to said printhead and said interconnect means provide interconnections extending generally transversely therebetween
In a preferred form the interconnect means is in the form of a tape automated bonded film (TAB film).
Desirably the TAB film electrically connects with said busbars by means of correspondingly sized noble metal deposited strips formed on sad TAB film.
Preferably the interconnect means also includes a plurality of control lines for correction to selected other of said voltage supply points on said printhead.
The unit can be detachable from the power supply and the external series of control lines. The conductive rails can comprise two mechanically stiff conductive bars.
In accordance with an eleventh aspect of the invention there is provided an ink supply unit for supplying a printhead containing an array of ink ejection nozzles, said supply unit comprising:
a first member formed having dimensions refined to a first accuracy and having a first cavity defined therein;
a second member in the form of an ink distribution manifold having a second cavity defined therein, said second cavity being adapted for the insertion of a printhead;
said second member being configured to engage said first cavity in said first member so as to define one or more chambers for the supply of ink to ink supply passages formed in said printhead;
said second member being formed having dimensions refined to a second accuracy which is higher than said first accuracy.
Preferably, the first and second members are configured to together define a series of ink storage chambers, desirably suitable for storing different colored inks.
In the preferred form the second member defines a series of discrete ink outlets that are adapted to provide ink to ink supply passages in the printhead that are adapted to supply ink to grouped sets of ink ejection nozzles.
Preferably, the second member has overall external dimensions that are substantially smaller than those of the first member.
In accordance with additional aspect of the eleventh aspect of the present invention, there is provided an ink supply unit for supplying a multiple color pagewidth ink supply printhead, comprising: a first elongated member containing a series of chambers for the storage of separate color inks and formed having dimensions refined to a first accuracy and having a first elongated cavity defined therein; a second elongated member including a series of wall elements and a second elongated cavity defined therein, the second elongated cavity being adapted for the insertion of a page width ink jet printhead, the wall elements mating with corresponding elements of the first elongated member to complete the formation of the series of chambers for the supply of ink to a series of slots formed in the back of the printhead when inserted in the second elongated cavity, wherein the second elongate member is formed having dimensions refined to a second accuracy which is higher then the first accuracy.
A screen for filtering portions of the ink supply flowing through to the printhead is preferably provided, optionally as part of the second member.
The first elongated member and/or the second elongated member can include a series of baffles for reducing the acceleration of the ink within the ink supply unit.
In accordance with a twelfth aspect of the present invention, there is provided a method of interconnecting a printhead containing an array of ink ejection nozzles to an ink distribution manifold, said method comprising:
attaching said printhead to said ink distribution manifold utilizing a resilient adhesive adapted to be elastically deformed with any deflections of the ink distribution manifold.
In accordance with an additional aspect of the twelfth aspect of the invention there is provided a printed and ink distribution manifold assembly wherein said printhead is attached to said ink distribution manifold by means of a resilient adhesive adapted to be elastically deformed with any deflections of the ink distribution manifold.
In the preferred form the printhead is an elongate pagewidth printhead chip and the ink distribution manifold forms part of an ink supply unit. Desirably the ink supply unit comprises:
a first elongated member containing a series of chambers for the storage of separate color inks and having a first elongated cavity defined therein;
a second elongated member including a series of wall elements and a second elongated cavity defined therein, said second elongated cavity being adapted for the insertion of a page width inkjet printhead, said wall elements mating with corresponding elements of said first elongated member to complete the formation of said series of chambers for the supply of ink to a series of slots formed in the back of said printhead when inserted in said second elongated cavity,
wherein said second elongated member is interconnected to said fist elongated member utilizing a resilient adhesive adapted to be elastically deformed with any bending of said ink supply unit.
The printhead chip can be attached to the ink supply unit along the sides and along a back surface thereof.
In accordance with a thirteenth aspect of the present invention, there is provided an inkjet printhead comprising.
a plurality of nozzle chambers, each having a nozzle aperture defined in one wall thereof for the ejection of ink out of said aperture;
an ink supply channel interconnected with said nozzle chamber;
a paddle moveable within the nozzle chamber by an actuator and operable to eject ink from said nozzle chamber, said paddle having a projecting part which, upon operation of said actuator is caused to move towards said nozzle aperture.
Preferably the projecting part upon activation of the actuator, moves through the plane of the aperture and can be located concentrically with the nozzle aperture.
The liquid ejection aperture can be formed utilizing the deposition and etching of a series of layers and the projecting part can comprise a hollow cylindrical column.
The hollow cylindrical column preferably can include an end adjacent temperature which can be chemically mechanically planarized during the formation of the aperture.
The actuator can comprise a thermal bend actuator conductively heated so as to cause movement of the paddle.
The projecting part can be located substantially centrally on the paddle.
In accordance with an additional aspect of the thirteenth aspect of the present invention, there is provided in an inkjet printhead having at least one chamber from which liquid is ejected from a nozzle aperture interconnected with said chamber by means of movement of a liquid ejection paddle, a method of improving the operational characteristics of said printhead comprising the steps of:
locating a projecting part on said moveable paddle, said projecting part undergoing movement towards said nozzle aperture upon activation of said liquid ejection paddle to eject fluid.
The projection part preferably can include an end portion which moves through the plane of an outer rim of the aperture upon activation of the liquid ejection paddle.
In accordance with a fourteenth aspect of the present invention, there is provided an inkjet printhead apparatus comprising:
a plurality of nozzle chambers each having a nozzle aperture defined in one wall thereof for the ejection of ink out of said chamber and a second aperture for the insertion of an actuator mechanism;
an ink supply channel interconnected with said nozzle chamber; a paddle moveable by an actuator operable to eject ink from said nozzle chamber, said actuator including:
a first portion located externally of said nozzle chamber and
a second portion located internally of said nozzle chamber, supporting said paddle;
an interconnecting portion interconnecting said first portion and said second portion through said second aperture, said interconnecting portion further including a protruding shield formed adjacent said second aperture and positioned so as to restrict the flow of fluid through said second aperture.
The shield can comprise a hydrophobic surface. The interconnecting portion typically moves in an upwardly defined direction towards the liquid ejection aperture, and the shield can be formed on a top surface of the portion. The actuator preferably can include a thermal expansion actuator located in the first portion.